This invention relates to pulsed lasers. Specifically it pertains to lasers that can be pulsed repeatedly within a relatively short period of time.
Laser designation systems have pointed out the need for fast, high power multiple pulsed lasers. FIG. 1 shows a typical prior art multiple pulse laser. The system shown in FIG. 1 is designed to produce a pulse from each Q-switch. U.S. Pat. No. 3,613,024 issued to Geusic et al. shows how Q-switches have been used to maximum effectiveness in pulsed lasers. Q-switches can be subject to reasonably fast times. However, in being used with fast repetition rates, they are subject to a high power density. The low damage threshold of conventional silica Q-switches limits laser power.
It has been shown by Scott et al, "Fast Acousto-Optic Lens Q-Switch", Journal of Applied Physics, Vol. 46, No. Aug. 8, 1975, that acousto-optic cells using cylindrically divergent light have an on time proportional to the inverse of bandwidth. It was further shown that the focused spot from such a cell travels at a velocity equal to twice the velocity of sound in the cell. These, properties have only been applied to single pulse Q-switches.
A further limitation for high power systems is that high voltage electro-optic Q-switches require high voltage with relatively long recharging times. Cross polarizers have been used to create multiple Q-switches, but practical size considerations limit the system to two pulses.
An improved chirped acousto-optic Q-switch is contained in U.S. Pat. No. 4,105,953 by J. Jernigan.